Impact printing mechanism

ABSTRACT

An impact printing mechanism comprising a pair of elements which move oppositely of each other so that the algebraic sum of the momenta of the elements is null during their motion and at the instant of impact of one of the elements on an associated printing plate.

United States Patent Inventor Armin Wirth Zurich, Switzerland App]. No. 765,473 Filed Oct. 7, 1968 Patented July 27, 1971 Assignee Wirth Gallo 8: Co.

Zurich, Switzerland Priority Jan. 11, 1968 SwitzerIand 586/68 IMPACT PRINTING MECHANISM 3 Claims, 5 Drawing Figs.

0.8. CI 1. 101/287, 101/93 R Int.Cl B41f1/38, B4lj 9/26 Fieidoisearch 101/93, 93

[56] References Cited UNITED STATES PATENTS 2,687,088 8/1954 Hennessy et a1. 101/95 2,895,411 7/1959 Demer et a1. 101/93 2,922,361 1/1960 Adler et a1 101/95 3,094,064 6/1963 Pecchenino 101/93 3,152,540 10/1964 Pensavecchia et a1 101/93 3,308,749 3/1967 Dowo 101/93 Primary ExaminerWil1iam B. Penn Atlomey-Stevens, Davis, Miller & Mosher ABSTRACT: An impact printingmechanism comprising a pair of elements which move oppositely of each other so that the algebraic sum of the momenta of the elements is nu1Iduring their motion and at the instant of impact of one of the elements on an associated printing plate.

SHEET 1 [IF 2 INVENTOR HRH/IV W/RTI/ HTTDRIVEyS PATENTEU m2? l97| IMPACI PRINTING MECHANISM The present invention relates to an impact printing mechanism, comprising a printing table, paper guides and type bearing members.

Impact printing mechanism are printing mechanisms in which a movable element, such as a type face, is accelerated and strikes a stationary element (such as a cylinder or printing table), the impression (for instance by transfer of ink from an inked ribbon) being produced substantially by the energy stored in the moving element when the latter strikes the stationary element and thereby producing the impression. A typical representation of such a printing mechanism is a typewriter, whereas a platen press is a representative of a machine using the contrary process, i.e. the direct application of force for the generation of the impression.

In the above-mentioned impact mechanism of a typewriter a hammer (the typeface and type lever) with a reduced mass of about 6 grams is accelerated. The hammer strikes an anvil (the cylindrical platen and components of the carriage or frame etc. which has at least a hundred times this mass. The impact transfers not more than a ten-thousandth of the energy of the hammer-to the anvil." This means that the vibrations of said components and of the entire machine due to the impact of the hammer are very small.

For various reasons these arrangements cannot be directly applied to a printing'mechanism which simultaneously prints a large number of characters, as is the case in price computing weighing machines for instance for shop counter or prepacking work. In such machines not only digits indicating weight, unit price, and price, i.e. their numerical values, but also the date and a code number aswell as the description of goods and makers name must be printed, requiring an impression comprising a total of about 60 letters and/or symbols. It is irrelevant to the description that follows whether the typefaces are attached to the hammer" or to the anvil."

It will be readily understood that the above-mentioned favorable relationship between hammer and anvil cannot be achieved in such circumstances. The indicating and printing mechanism and a weighing machine which may be attached thereto would suffer excessive vibration.

Price computing printing weighing machines of conven tional kind are of heavy construction. They may be provided with a preferably statically working printing mechanism in which case they operate rather slowly. Possibly the impression is produced in several stages, i.e. parts of the impression, such as the description of the goods, is not printed at the same time as the numerical values, or the maker's name is preprinted on the paper tape. Owing to the generation of noise and the complications of the design, such weighing machines are usually used only as prepacking weighing machines. Printing is effected relatively deep inside the casing, a fact which in turn requires a complicated and time-consuming transportation of the voucher to the outside.

It is the object of the present invention to provide a printing mechanism, which is capable of simultaneous printing of a large number of characters, in an extremely short time (for instance in 0.01 seconds) without generating troublesome noise and vibration, and in which the impression can be produced near the casing wall, that is to say in a position in which the voucher is readily accessible to the vendor or purchaser. The size and power required are to be a minimum, permitting the printing mechanism to combined in a unit together with the setting, computing and display mechanism and mounted on a thin column which occupies little space on a counter and does not obstruct direct vision between the vendor and the purchaser.

It is another object of the invention to provide an impact printing mechanism, comprising a frame, a printing surface, type bearing members, two impact elements movably mounted in said frame with one degree of freedom and coupled to each other, a paper supply, a paper feeding device guiding said paper between said printing surface and one of said movable elements, said tyne bearing members being also mounted between said printing surface and one of said movable elements, so that impression is produced by the impact of one of said elements on the printing surface and that the algebraic sum of the momenta of both movable elements and that of the moments of their momenta is nil at the instant of impact. Embodiments of the invention are schematically illustrated in the accompanying drawings in which FIG. I is a first embodiment comprising gliding elements,

FIG. 2 is a second embodiment comprising contrarotating elements,

FIG. 3 is a third embodiment with corotating elements,

FIG. 4 is a fourth embodiment with rotating elements whose center of gravity is in the axis of rotation, and

FIG. 5 is a modification of said fourth embodiment.

Referring to FIG. I this shows the frame 1 of one embodiment of the proposed printing mechanism. This frame 1 contains two substantially like elements 2 and 3 of equal mass. Each is formed with a projection 4 provided with rack teeth 5. A bore 6 inside the projection 4 contains a spring 7 which extends into a bore 8 in the second element. The two sets of rack teeth 5 mesh with a pinion 9 on a shaft 10 mounted in the frame 1. The elements 2 and 3 are formed with recesses 11 which are of such a size that the centers of gravity of the two elements 2 and 3 move along a straight path A-A intersecting the shaft 10 parallel to two guiding surfaces 12 and 13.

The element 3 has a further recess 14 containing a spring 15 which bears against the rear wall 16 of the frame 11.

Moreover, a lever 17 formed with a tooth 18 is pivotably attached to the frame l and biased by a spring 19 in the clockwise direction. The left-hand end of the frame 1 forms a printing table 20 supporting a type block 21. The paper tape that is to be printed upon is inserted into a slot 22.

The described mechanism functions as follows:

The shaft 10 couples the pinion 9 to a cocking mechanism not shown in the drawing and for transferring the mechanism into a position ready for printing the pinion is rotated clockwise. When the end faces of the two elements 2 and 3 reach the positions 2a and 3a shown in dot-dash lines the tooth I8 snaps into engagement and retains the two elements 2 and 3 in these positions. For releasing the mechanism to produce an impression after the paper tape has been inserted into the slot the lever 17 is simply depressed against the action of spring I9. The springs7 will then accelerate the two elements 2 and 3 outwards. The end face of element 2 strikes the type block 21 and an impression is made on the tape. In their decompressed state the two springs 7 still provide slight freedom of movement which is taken up by the much weaker spring 15 which after impact slightly retracts the two elements 2 and 3 inwards to permit the paper tape to be withdrawn. In this embodiment the masses of the two elements 2 and 3 and their motions are completely alike. The forces required for accelerating the two elements 2 and 3 are continuously equal and since they act in contrary directions their reactions cancel each other out. The algebraic sum of the momenta of the two elements is nul during their motion and at the instant of impact. As the elements 2 and 3 are not rotating the algebraic sum of the moments of their momenta is also always nul.

In the embodiment according to FIG. 2 the two elements 102 and 103 have the form of double-armed levers. Each lever is fulcrumed on a shaft 23. The two shafts 23 are mounted in a frame 101 and they are coupled with a cocking mechanism not shown in the drawing. The shorter lever arms 24 of the two elements 102 and 103 have the form of toothed sectors 25 which are in permanent mesh. One end of a leaf spring 26 engages a notch 27 in the element 103, whereas its other end engages a notch 28 in the frame 101. A tension spring 29 connects the two elements 102 and I03. This spring opposes the elastic thrust of the leaf spring 26. A pawl 31 is mounted on the front wall 30 of the frame I01. This pawl 31 is biased in anticlockwise direction by a spring 32 and extends through a gap 33 in the front wall 30. A type block is affixed to a printing table 20 affixed to the frame 101. Moreover, type wheels 34 are mounted on a shaft 35. These are set according to the variable measured and/or input quantity. A roll of paper tape 36 is likewise mounted in the frame 101 and delivers the paper tape 37. The tape runs between the typewheels 34, the type block 21 and the element 102 to an exit slot 22. A cutter mechanism not shown in the drawing permits the paper tape to be cut at the same time as the impression is produced or immediately afterwards. The disposition of an inking ribbon and of the paper feed is conventional, and these elements have been omitted to avoid complication.

The described arrangement functions as follows:

The mechanism is transferred into position ready for printing by deflecting the two elements 102 and 103 in contrary directions against the resistance of the leaf spring 26 by the cocking mechanism. The two elements 102 and 103 will then assume the positions 1020 and 103a, indicated in a dot-dash lines and the leaf spring 26 will be in position 260. The pawl 31 engages and retains the two elements 102 and 103 in this deflected position. At the same time the typewheels 34 are set and the paper feed started. In order to achieve printing pawl 31 is released at the desired instant. The two elements 102 and 103 are so designed that, in printing position, the radii of their centers of gravity 38 are equal and perpendicular to the line connecting the two shafts 23. The length of the arms 24 is so chosen that the kinetic energy of both elements 102 and 103 is substantially identical. The algebraic sum of the momenta of the two elements and that of the moments of their momenta are nul at the instant of impact.

In the embodiment illustrated in FIG. 3 the two elements 202 and 203 are mounted on shafts 39. A leaf spring 26 extends between a notch 27 in the element 203 and a notch 28 in the frame 201. The two elements 202 and 203 are coupled by two links 40 which are themsleves attached to the frame I by another link 41. The three links are all hinged on a common hinge pin 42. The other components correspond to similar components in FIG. 2, the paper roll and the pawl being omitted for the sake of simplicity. Again in this embodiment the algebraic sum of the momenta of the two elements and that of the moments of their momenta is nil in printing position.

FIG. 4 shows yet another embodiment in which the element 302 is a lever, whereas the element 303 is a cylinder. The centers of gravity of both elements coincide with the centers of two shafts 39. The two elements 302 and 303 have intermeshing toothed sectors 25. The cocking spring and the pawl are algebraic sum of the moments of their momenta is nil. Since the centers of gravity of the two elements coincide with their fulcra, the algebraic sum of their momenta is likewise nil.

In all the above embodiments the impression is produced between a printing table and one element. However, the impression might also be produced between the two elements. This possibility is schematically illustrated in FIG. 5. The two elements 402 and 403 are deflectably mounted on their respective shafts 39. It is assumed that the masses of the two elements 402 and 403 are equal and equally distributed, so that the path lengths of the printing surfaces 43 are likewise equal. The type faces 44 are provided on a bar 44 which is adjusted according to the particular character that is to be printed. Instead of a bar 44 printing blocks might be provided. The bar 44 is yieldingly held for instance by a small spring force approximately midway between the two impact surfaces 43. For creating the impression the bar is impacted simultaneously from each side by the two impact faces 43. Conveniently the type bar is a low mass element which may consist for instance of polyamide.

FIGS 2 and 4 illustrate the use of a paper tape withdrawn from rolls. However, the paper may be provided in the form of a paper pile, or a weigh card may be inserted for each weighing.

lclaim:

1. An impact printing mechanism comprising in combination a frame, a printing surface, a type bearing member, a plurality of elements movably mounted within said frame, said elements coupled to each other with one degree of freedom, said type bearing member being mounted between said printing surface and said movable elements, and means causing a first one of said movable elements to strike said type bearing member and a second one of said movable elements to move simultaneously with said first one of said movable elements and with substantially the same inertial force substantially the same distance in a substantially opposite direction from said first element and away from said type bearing member.

2. An impact printing mechanism according to claim 1, further comprising means to retract said first movable element from said printing position.

3. An impact printing mechanism according to claim 2, wherein said striking and retracting means comprise springs. 

1. An impact printing mechanism comprising in combination a frame, a printing surface, a type bearing member, a plurality of elements movably mounted within said frame, said elements coupled to each other with one degree of freedom, said type bearing member being mounted between said printing surface and said movable elements, and means causing a first one of said movable elements to strike said type bearing member and a second one of said movable elements to move simultaneously with said first one of said movable elements and with substantially the same inertial force substantially the same distance in a substantially opposite direction from said first element and away from said type bearing member.
 2. An impact printing mechanism according to claim 1, further comprising means to retract said first movable element from said printing position.
 3. An impact printing mechanism according to claim 2, wherein said striking and retracting means comprise springs. 